1. Field of the Invention
This invention relates to a method of forming a moire pattern of contour lines representing the three dimensional surface configuration of an object, and more particularly to a method of obtaining moire contour lines of a large object by use of light scanning means.
2. Description of the Prior Art
It has been known in the art to obtain a moire pattern of contour lines representing the three dimensional surface configuration of an object. In one conventional method of obtaining moire contour lines, a grating is placed in front of the object to form a shadow of the grating on the surface of the object. The shadow of the grating is distorted by the surface of the object and forms a moire pattern when superposed with said grating. In another conventional method, the image of a grating is projected through a projection lens system onto the surface of the object. The image projected on the object is distorted by the surface of the object and forms a moire pattern when superposed with said grating. In both the known methods, it is difficult to obtain a moire pattern representing the surface configuration of a large object. In the former method, the grating must be as large as the object. In the latter method, the larger is the object, the more difficult it is to prepare a projection lens system which is capable of enlarging the image of the grating to the required size. Further, in the latter method, the pitch of the grating cannot be reduced beyond the certain limit because of the diffraction phenomenon.